GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
True, but you see his design follows the Shinden's configuration closer than the hypothetical single-engined Do335 or the XP-55
S/E lightweight Pusher Do 335.
- Thread starter wuzak
- Start date
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GregP
Major
Hi FlyboyJ,
The design may not BE at fault.
There is a small Aluminum plate that is fiberglassed into place where the bolts screw in with nuts or nutplates. The correct procedure is to trim the excess glass right as the resin sets with a razor blade or other sharp edge. Unfortunately, if you push too hard, you can score the Aluminum plate, making for a stress riser around the mounting holes. Not saying that is what happened, I am saying the basic design and construction lend themselves to this issue and THAT is not good. Far better to have a design that cannot CAUSE a stress riser, and it would be an easy change to make.
Our friends might have simply done some aerobatics and might have over-g'd the plane ... nobody knows; we sure don't. We found the wreckage after they became overdue on a day with LOTS of heavy turbulence warnings around the area.
Of course, I also helped find the wreckage of an Extra 300 once and we found one aileron spade more than 400 yards from the main crash site. Probably had a LOT to do with the crash. So, it isn't all Rutan canards by any means.
Still, I am not happy that the design allows you to make a critical mistake that cannot be easily checked or rpaired if you find scoring on the plate. Prior to coming to the Planes of Fame I was a Rutan canard fan. Not so much these days, especially after having gotten close to several and seen the workmanship or lack thereof in flying examples. Some are exquisite ... others look as though they were assembled by one-eyeed Spider Monkeys in too much of a hurry working without plans.
Whenever I fly in a homebuilt, I do a careful preflight with the owner. I have turned down the ride several times. Mostly the planes went on to long flight careers, not always. I have universally had a GREAT time when flying anything from Van's aircraft. I LOVE the RV-4,6,7,8 planes and would do almost anything legal to fly in a Harmon Rocket again ... especially from the front seat. 4,600+ fpm when flying solo and better than 4,200 fpm 2-up. That outclimbs a P-51 ... up to a point.
But back to the single engine Do 335. It would have to be a new design. It could certainly borrow from the Do 335, but the Do 335 was not feasible as a single engine design to my thinking. It was designed with two engines in mid from the outset, and the weight was such that it could handle that stress. Perhaps moving the wings might have been possible, but I rather think the spars would have interfered with the engine or at least the engine mount if they did. Better to start from scratch and use the knowledge to design a dedicated single-engine thing than to cobble up a heavy twin with half the originally-designed power level. That doesn't sound like a recipe for anything but failure.
Of course, it could have been otherwise ... I think not.
The design may not BE at fault.
There is a small Aluminum plate that is fiberglassed into place where the bolts screw in with nuts or nutplates. The correct procedure is to trim the excess glass right as the resin sets with a razor blade or other sharp edge. Unfortunately, if you push too hard, you can score the Aluminum plate, making for a stress riser around the mounting holes. Not saying that is what happened, I am saying the basic design and construction lend themselves to this issue and THAT is not good. Far better to have a design that cannot CAUSE a stress riser, and it would be an easy change to make.
Our friends might have simply done some aerobatics and might have over-g'd the plane ... nobody knows; we sure don't. We found the wreckage after they became overdue on a day with LOTS of heavy turbulence warnings around the area.
Of course, I also helped find the wreckage of an Extra 300 once and we found one aileron spade more than 400 yards from the main crash site. Probably had a LOT to do with the crash. So, it isn't all Rutan canards by any means.
Still, I am not happy that the design allows you to make a critical mistake that cannot be easily checked or rpaired if you find scoring on the plate. Prior to coming to the Planes of Fame I was a Rutan canard fan. Not so much these days, especially after having gotten close to several and seen the workmanship or lack thereof in flying examples. Some are exquisite ... others look as though they were assembled by one-eyeed Spider Monkeys in too much of a hurry working without plans.
Whenever I fly in a homebuilt, I do a careful preflight with the owner. I have turned down the ride several times. Mostly the planes went on to long flight careers, not always. I have universally had a GREAT time when flying anything from Van's aircraft. I LOVE the RV-4,6,7,8 planes and would do almost anything legal to fly in a Harmon Rocket again ... especially from the front seat. 4,600+ fpm when flying solo and better than 4,200 fpm 2-up. That outclimbs a P-51 ... up to a point.
But back to the single engine Do 335. It would have to be a new design. It could certainly borrow from the Do 335, but the Do 335 was not feasible as a single engine design to my thinking. It was designed with two engines in mid from the outset, and the weight was such that it could handle that stress. Perhaps moving the wings might have been possible, but I rather think the spars would have interfered with the engine or at least the engine mount if they did. Better to start from scratch and use the knowledge to design a dedicated single-engine thing than to cobble up a heavy twin with half the originally-designed power level. That doesn't sound like a recipe for anything but failure.
Of course, it could have been otherwise ... I think not.
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l'Omnivore Sobriquet
Airman 1st Class
Forget about the Narval ("Narwhal", some sort of swordfish), pilots could hardly control the ship in some configuration, and it was meant to be a carrier born fighter !
Although looking good : Google Image Result for http://www.avionslegendaires.net/wp-content/uploads/images/avion_militaire/Gnarval.jpg
A typical exemple showing the delais due to the freezing of French aeronautical development for 4 crucial years. Together with the Arsenal VB-10 it should be added, this one ridiculed by... that Do-335 again (the B1), that was being extensively tested in meantime.
Both aircraft, Narval and VB-10 were abandonned, but not that quickly : because although doomed, the authorities let the burgoing air industry make its own teeth on something, that at least existed for sometimes, rather wisely.
In every field you can think of, French aeronautics was utterly shattered in 1945. Even the Japanese was in better shape in september 45 ! (clue : France got more bomb tonnage during WWII than the UK, and guess what were the favorite targets ? Plus total forbiddence from the Germano-Italian armistice commission to undertake any serious home work from mid-1940 onwards.) Anyway the story of the French reborn from 1945 to 1958 is a most fascinating one, I repeat here.
Was just wishing to conclude with an outsider on the topic !
Do you know the Potez 75 of the mid-50's ?
A rather successfull design, very rustic, a quite small pusher aircraft of some African 'Coin' dedication, with one 'weapon master' sitting in front behind some bus-like windows, the pilot up and above in open air à l'ancienne and yes, fixed undercarriage ?
By an Apache, something like a soap-box car next to a Dodge 6x4.
Sorry cannot copy and paste (right-click disease currently), but here are picture links :
Google Image Result for http://www.avionslegendaires.net/wp-content/uploads/images/avion_militaire/Gpotez75.jpg
Ugly isn't it ?
Some more : http://www.google.com/imgres?imgurl...ATUvmIL4a00QWK_IH4Dw&ved=0CDMQ9QEwAg&dur=1136
Potez 75 | www.avionslegendaires.net
And the en. wiki : Potez 75 - Wikipedia, the free encyclopedia
Well it flew very well.
And the prototype gave extreme satisfaction when deployed in operation in Algeria.
Which is why you can be certain, Parisian authorities cut immediately further fundings.
And yes the Shinden is such an appealing aircraft....
Although looking good : Google Image Result for http://www.avionslegendaires.net/wp-content/uploads/images/avion_militaire/Gnarval.jpg
A typical exemple showing the delais due to the freezing of French aeronautical development for 4 crucial years. Together with the Arsenal VB-10 it should be added, this one ridiculed by... that Do-335 again (the B1), that was being extensively tested in meantime.
Both aircraft, Narval and VB-10 were abandonned, but not that quickly : because although doomed, the authorities let the burgoing air industry make its own teeth on something, that at least existed for sometimes, rather wisely.
In every field you can think of, French aeronautics was utterly shattered in 1945. Even the Japanese was in better shape in september 45 ! (clue : France got more bomb tonnage during WWII than the UK, and guess what were the favorite targets ? Plus total forbiddence from the Germano-Italian armistice commission to undertake any serious home work from mid-1940 onwards.) Anyway the story of the French reborn from 1945 to 1958 is a most fascinating one, I repeat here.
Was just wishing to conclude with an outsider on the topic !
Do you know the Potez 75 of the mid-50's ?
A rather successfull design, very rustic, a quite small pusher aircraft of some African 'Coin' dedication, with one 'weapon master' sitting in front behind some bus-like windows, the pilot up and above in open air à l'ancienne and yes, fixed undercarriage ?
By an Apache, something like a soap-box car next to a Dodge 6x4.
Sorry cannot copy and paste (right-click disease currently), but here are picture links :
Google Image Result for http://www.avionslegendaires.net/wp-content/uploads/images/avion_militaire/Gpotez75.jpg
Ugly isn't it ?
Some more : http://www.google.com/imgres?imgurl...ATUvmIL4a00QWK_IH4Dw&ved=0CDMQ9QEwAg&dur=1136
Potez 75 | www.avionslegendaires.net
And the en. wiki : Potez 75 - Wikipedia, the free encyclopedia
Well it flew very well.
And the prototype gave extreme satisfaction when deployed in operation in Algeria.
Which is why you can be certain, Parisian authorities cut immediately further fundings.
And yes the Shinden is such an appealing aircraft....
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davebender
1st Lieutenant
Why not two DB605 engines which were in plentiful supply by 1944? Even late war DB605ASM was considerably lighter in weight then DB603. Liquid cooling system should be lighter too. If 3,600 total hp isn't enough for good performance then you need to put the airframe design on a diet.
GregP
Major
Hi l'Omnivore Sobriquet,
I am familiar with the Potez, but was NOT familiar with the flight characteristics at all. Since my heritage is a large part French (last name is Pascal), I am well versed in the French aircraft that got built, but less so in their final flight characteristics or reasons for non-adoption. The lineage of the various French aircraft firms is interesting and somewhat confusing to an outsider, but their planes generally few well even if sometimes being of strange-looking design. I did not mention the VB-10 or the Latecoere Late 299A since we were talking about either single engine pushers or tandem centerline thrust twins.
The generally good-flying planes do NOT include the SNCASE 1010 or probably the Payen series of designs ... though I don't really know about the Payens. For a strange looking French plane, the SIPA S.1100 is rght up there in my book.
To me the best-looking French jet fighter that ever flew was the Mirage F.1, but that's just me. I also really like the Mirage 4000, even though it was never sold to anyone including the French. My favorite large flying boat was the Latecoere 631 though I would have preferred it to be made from metal rather than wood. Very art-deco. I can imagine having French cuisine and sipping wine while flying the Atlantic at 2 - 3,000 feet waving at ships as we stately pass by at 200 mph just AFTER the war.
So I believe a rear engine pusher was possible, but not using components taken directly from the Do 335. The wings themselves were probably too big and heavy for a single-engine fighter. Better to start from scratch and design something from the outset for single engine operation, possibly using knowledge gained from the Do 335. If the war had continued, I have no doubt the Do 335 would have joined. How successful it might be is another what-if.
Myself, I would NOT have used the layout for a piston aircraft in any conceivable circumstances if I were in charge of design ... unless the customer asked for it specifically. I doubt you'd encounter that.
I am familiar with the Potez, but was NOT familiar with the flight characteristics at all. Since my heritage is a large part French (last name is Pascal), I am well versed in the French aircraft that got built, but less so in their final flight characteristics or reasons for non-adoption. The lineage of the various French aircraft firms is interesting and somewhat confusing to an outsider, but their planes generally few well even if sometimes being of strange-looking design. I did not mention the VB-10 or the Latecoere Late 299A since we were talking about either single engine pushers or tandem centerline thrust twins.
The generally good-flying planes do NOT include the SNCASE 1010 or probably the Payen series of designs ... though I don't really know about the Payens. For a strange looking French plane, the SIPA S.1100 is rght up there in my book.
To me the best-looking French jet fighter that ever flew was the Mirage F.1, but that's just me. I also really like the Mirage 4000, even though it was never sold to anyone including the French. My favorite large flying boat was the Latecoere 631 though I would have preferred it to be made from metal rather than wood. Very art-deco. I can imagine having French cuisine and sipping wine while flying the Atlantic at 2 - 3,000 feet waving at ships as we stately pass by at 200 mph just AFTER the war.
So I believe a rear engine pusher was possible, but not using components taken directly from the Do 335. The wings themselves were probably too big and heavy for a single-engine fighter. Better to start from scratch and design something from the outset for single engine operation, possibly using knowledge gained from the Do 335. If the war had continued, I have no doubt the Do 335 would have joined. How successful it might be is another what-if.
Myself, I would NOT have used the layout for a piston aircraft in any conceivable circumstances if I were in charge of design ... unless the customer asked for it specifically. I doubt you'd encounter that.
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l'Omnivore Sobriquet
Airman 1st Class
Just call me l'O.S
Shortround6
Major General
Ah yes, the DB605ASM Wundermotors. The ones that were good for 1250ps at sea level for a 30 min climb rating compared to the DB603A 1580 hp (PS?) climb rating at sea level. Or the 1020PS max cruise at sea level compared to the DB 603A's 1375hp (PS?) max cruise?
If you plan to fly the Do 335 with those engines you had better put the airframe on a serious diet.
- Thread starter
- #48
wuzak
Captain
Certainly won't save as much weight as you would dumping one of the DB603s.
A DB604 or DB609 may have had enough power - but they didn't go into production. Or a Jumo 222. Also a very problematic engine.
A DB606 or DB610 could have worked - but would require too much modification - because of the extra width.
Dornier's next proposed twin "Otto" engine aircraft was the P.252. This had the two DB603s mounted in tandem with (IIRC) the fuel tank between them, each driving a pusher prop at the end of teh tail. The cockpit was moved closer to the front of the aircraft.
Regarding weight balance - did the Do 335's tail planes give lift or down force? If it was the latter than perhaps changing to lifting tail surfaces would resolve some of the CoG/CoL issues?
GregP
Major
It was a conventional layout, not a canard, so they gave downforce.
OldSkeptic
Senior Airman
- 509
- May 17, 2010
Both the Do-335 and the He-1777 had overheating (and fire) problems with their rear engines (the 177 having 2 coupled engines). I suspect that the issue is complexity, of the exhaust, cooling and fuel systems (as well as control runs running through the engine bay).
Don't forget, even with liquid cooling the exterior of the engine gets very hot, with an engine in the front you do get a cooling effect from heat transferring to the cowling and being cooled by the air.
This is reduced with a rear engine, hence you are going to get a pretty hot engine bay.
Of course it can be dealt with (eg the P-39), but the German experience shows that it was difficult to get right.
- Thread starter
- #51
wuzak
Captain
The He 177 didn't have a "rear" engine. It had coupled DB 601s or DB605s, which were side by side, not tandem.
The Do 335's exhausts weren't complicated.
http://star.ap.teacup.com/alfaromeogt/img/1256048597.jpg
Look to be as complicated as the front engine's exhaust.
It would also appear, from that cutaway, that the engine could be moved forward above the wing, without affecting the spars. The fuel tanks would need relocating, perhaps (partially) to the bomb bay.
The Do 335's exhausts weren't complicated.
http://star.ap.teacup.com/alfaromeogt/img/1256048597.jpg
Look to be as complicated as the front engine's exhaust.
It would also appear, from that cutaway, that the engine could be moved forward above the wing, without affecting the spars. The fuel tanks would need relocating, perhaps (partially) to the bomb bay.
swampyankee
Chief Master Sergeant
- 4,031
- Jun 25, 2013
You mean redesign it to a tandem-wing configuration (see the Quickie)? A aircraft with a conventional configuration and a lifting tail is unstable.
davebender
1st Lieutenant
This aircraft will perform just fine powered by a pair of DB605 engines and design was production ready by 1940.
OldSkeptic
Senior Airman
- 509
- May 17, 2010
True thanks for that .... mental slip. But it still got very hot, hence all the fire problems.
- Thread starter
- #55
wuzak
Captain
That wasn't the only problem.
There were, apparently, some issues with late DB603s spitting out their spark plugs. That is what happened to one British test pilot testing a Do 335 after the war.
GregP
Major
I don't think it got very hot. The same water pumps were used and the same cooling formulas were used.
I think it leaked oil.
Puddled oil next to an exhaust pipe is a recipe for fire. The coupled engines made access to the center portion VERY difficult and put the oil level much higher than it would ordinarily be for the outer cylinder banks. If I had to make a guess, I'd guess the fires mostly started on the outboard side due to the high oil level there that was never designed for and probably not seen as an issue.
That is, of course, just a guess. Maybe they DID get hot. If so, why? the radiator capacity was well known and the water pumps were also well known. The coupled engines weren't running any harder either.
So an oil issue seems logical because the engines were never designed to run while flying in a 60° bank continuously.
I think it leaked oil.
Puddled oil next to an exhaust pipe is a recipe for fire. The coupled engines made access to the center portion VERY difficult and put the oil level much higher than it would ordinarily be for the outer cylinder banks. If I had to make a guess, I'd guess the fires mostly started on the outboard side due to the high oil level there that was never designed for and probably not seen as an issue.
That is, of course, just a guess. Maybe they DID get hot. If so, why? the radiator capacity was well known and the water pumps were also well known. The coupled engines weren't running any harder either.
So an oil issue seems logical because the engines were never designed to run while flying in a 60° bank continuously.
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- Thread starter
- #57
wuzak
Captain
Speaking of the DB606 in the He 177 Greg?
I think the worst position was the inboard cylinders, since their exhausts pointed down, through the bottom of the nacelle, right where any leaking oil would gather.
DB606s didn't seem to have any issues in the Me 261 V1 in the few flights it undertook. I think largely it was an issue with the He 177 installation.
- Thread starter
- #58
wuzak
Captain
Isn't stability a matter of where the CoG is in relation to the lifting surfaces?
Shortround6
Major General
There is a radiated heat issue. The inside of the blocks may show normal temperature in the coolant but the space between the two inner cylinder banks is getting twice the heat (btu's not temp) that the space on either side of a normal inverted V-12 would see inside the cowling, throw in the exhausts (again not the normal straight to the outside exhausts) and you have a real 'cooker' in-between the inner banks.
get those exhaust pipes to practically glowing and I wonder what is does to the oil in the cam covers?
GregP
Major
Stability is an issue of where the center of lift (or aerodynamic center) is in relation to the center of gravity. In a conventional aircraft, the tail has downforce. If the tail has lift, the rear surfaces are MUCH larger and it is a tandem-wing aircraft. Here is a pic of a tandem-wing aircraft:
I'm sure you can see the difference between this and a conventional layout.
Thanks Wuzak, I meant inner cylinders (embarrassed) and got it backwards. The exhaust pipes didn't heat the cylinder heads much, but they were very close to puddled oil and the engine wasn't designed for oil at that level all the time, nor were the internal components. I could be wrong, but upright engines are NOT designed for a coutinuous 60° bank either ... unless they are intended for aerobatic use.
Warbirds were never intended for other than momentary aerobatic use. Most are cleared for 5 - 15 - 20 seconds at most, and many not cleared at all for negative-g.
I'm sure you can see the difference between this and a conventional layout.
Thanks Wuzak, I meant inner cylinders (embarrassed) and got it backwards. The exhaust pipes didn't heat the cylinder heads much, but they were very close to puddled oil and the engine wasn't designed for oil at that level all the time, nor were the internal components. I could be wrong, but upright engines are NOT designed for a coutinuous 60° bank either ... unless they are intended for aerobatic use.
Warbirds were never intended for other than momentary aerobatic use. Most are cleared for 5 - 15 - 20 seconds at most, and many not cleared at all for negative-g.
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